The Latency screen appears this way because you have Aerodrums set to MIDI mode. In this mode, Aerodrums doesn't output audio itself, only MIDI notes. That's why the audio buffer size setting does not appear.

If you are using Aerodrums with a DAW or similar then you'd typically configure the buffer size and other audio settings within that software.

If you go to the MIDI screen and set Aerodrums back to "No MIDI" mode then the audio buffer size and other settings will reappear on the Latency screen.